A conventional stored chemical energy heat source is known in accord with U.S. Pat. No. 3,325,318 issued June 13, 1967 to Richard S. Pauliukonis and assigned to TRW, Incorporated. This patent teaches a stored chemical energy heat source wherein lithium metal is reacted with sulfur hexafluoride to produce lithium sulfide and lithium fluoride as well as heat energy. The teaching of U.S. Pat. No. 3,325,318 is that such a stored chemical heat source may be used in missiles, satellites, or torpedoes as well as direct thermal electric conversion devices. However, U.S. Pat. No. 3,325,318 does not otherwise deal with the details of applying the heat energy obtained from the chemical energy heat source in a practical application.
Another conventional teaching is set forth in the U.S. Pat. No. 3,964,416 issued June 22, 1976 to Raymond J. Kiraly, et. al., and assigned to the United States of America. The U.S. Pat. No. 3,964,416 teaches a stored chemical energy heat source wherein a fuel storage and reaction chamber also includes a heat exchanger. A mass of lithium metal is contained within the fuel storage and reaction chamber and is therein reacted with sulfur hexafluoride to produce heat and the reaction products mentioned earlier. The heat of this reaction is extracted from the fuel storage and reaction chamber via the integral heat exchanger consisting of a closed loop of heat transfer tubing conveying a flow of heat transport fluid therein.
While U.S. Pat. No. 3,964,416 would appear to effect a practical application of the chemical energy heat source taught by the earlier U.S. Pat. No. 3,325,318, it appears immediately that once the reactin chamber is utilized to provide heat, the lithium sulfide and lithium fluoride reaction products must be removed from the reaction chamber in order to allow its refueling and subsequent reuse. Alternatively, the reaction chamber can simply be discarded after removal of unreacted lithium fuel. Of course, this alternative presents the undesirable aspect of simply throwing away a complex and expensive structure which, were it possible to renew its fuel charge, would in all likelihood be useable to react several batches of fuel. It must be noted in this respect that the lithium fluoride and lithium sulfide reaction products of sulfur hexafluoride with the metallic lithium result in a rock-like or cement-like mass filling the reaction chamber. This mass of reaction products is not easily removed from the reaction chamber, and also contains unreacted lithium which presents environmental hazards if the reaction chamber is simply discarded after a single use.
In view of the above, the need is apparent in the pertinent art for the solution to the problem of refueling such a stored chemical energy reaction chamber wherein lithium metal or another metallic fuel is reacted with sulfur hexafluoride or another reactant.